1. Field of the Invention
The present invention relates generally to personal computer systems. More particularly, the present invention relates to cost effective methods and arrangements to upgrade a personal computer using a peripheral processor card.
2. Art Background
Personal computers have proliferated since their first availability, with an increasingly wide variety and selection of computers now offering many degrees of functionality, architecture, etc. One popular family of personal computers, the Macintosh.RTM. manufactured and sold by Apple Computer, Inc., has been built upon the 68000 family of microprocessors manufactured by Motorola, Inc. Since its introduction in 1984, the Macintosh.RTM. (registered trademark of Apple) has evolved from a small, user-friendly but slow computer having 128 kilobytes (kB) of system memory, to the large desktop and floor Quadra.RTM. models using the faster 68040 central processor unit (CPU) and having base system memory configuration of 8 megabytes (MB) expandable to 64 MB and beyond. Many millions of Macintosh computers have been sold and are in use throughout the world.
Apple, in adopting a new hardware architecture to carry forward into the next century, has selected the reduced instruction set computer (RISC) PowerPC.TM. architecture developed by International Business Machines (IBM) and implemented in the PC601 microprocessor (PowerPC is a trademark of IBM). Beginning in early 1994, Macintosh computers will all soon incorporate PowerPC microprocessors which, depending upon the code executing on it, will be many times faster than current state of the art Macintosh computers using the conventionally architected 68040 microprocessor. However, many owners and users of 040-based computers, particularly small business and home users, will not want to or be capable of immediately replacing their existing machines with the new PowerPC based machines. In such cases, it would be desirable to provide such users with an alternative, less costly but comparably functional conversion path, namely a peripheral add-in card which would effectively upgrade the existing computer system with PowerPC functionality.
Add-in peripheral processor cards have been used with considerable success to provide numerical computation acceleration, as well as cross-architecture or cross-platform computing solutions. One example of a cross-platform peripheral add-in card is the Orange card manufactured and sold by Orange Solutions, which incorporates a 80486-based microprocessor using the X86 architecture developed by Intel Corporation. When added to a 040-based computer, for example the Macintosh Quadra, the X86 peripheral card enables a user to run both application and utility programs on either processor. Peripheral cards typically include all interface, memory, and input/output (I/O) components in addition to the processor providing the essential function of the add-in card. However, such peripheral cards are inherently expensive because they necessarily include the cost of the associated circuit elements, which are duplicative to the components already present in the computer.
As will be described in the following detailed description, the present invention provides a cost effective arrangement for an optional, high performance PowerPC-based peripheral add-in card to be inserted into a 040-based personal computer. The peripheral card containing the PowerPC microprocessor functions so as to override the 040 processor present on the motherboard of the computer, while sharing essential functional components of the 040 system, such as memory and I/O, thus improving computer performance to the equivalent of a PowerPC computer.